I have asked this on other forums but no one seems to have an answer.
Can anyone (Bueller?... Bueller?... Bueller?) explain why people talk about a difference between the Alps and the Pyrenees and why particular riders a better suited to one rather than the other ?

I tihnk there may be lots of reasons...spanish riders love them as there is a load of orange jersey wearing fanatics pushing them up hill...(in spirit or actually doing it).A bit like levi's umm mechanical helping hand,at least you would think the mechanic would have tried to look like he was adjusting his saddle instead of blatantly pushing him and smiling at the TV camera.Also I think the gradients are easier in the Alps,yes they go higher but they are not as sharp in general....so much harder to keep a rythm hence the pure climbers can vary the pace with attacks which blow the guys just holding on.

Generally speaking, the Alps are long, steady climbs. The Pyrenees are shorter but steeper, hence the two different styles needed. The Pyrenees are also a lot more barren and, being right next to Basque territory, unless you are wearing Orange, you are an enemy alien - the Basques love their cycling, are very parochial and come out in force.